# Define here the models for your spider middleware
#
# See documentation in:
# https://docs.scrapy.org/en/latest/topics/spider-middleware.html
import scrapy.crawler
from scrapy import signals

# useful for handling different item types with a single interface
from itemadapter import is_item, ItemAdapter
from scrapy.http import HtmlResponse
from selenium import webdriver
from selenium.common import TimeoutException
from bs4 import BeautifulSoup


class SipderworkscrapySpiderMiddleware:

    @classmethod
    def from_crawler(cls, crawler):
        # This method is used by Scrapy to create your spiders.
        s = cls()
        crawler.signals.connect(s.spider_opened, signal=signals.spider_opened)
        return s

    def process_spider_input(self, response, spider):
        # Called for each response that goes through the spider
        # middleware and into the spider.

        # Should return None or raise an exception.
        return None

    def process_spider_output(self, response, result, spider):
        # Called with the results returned from the Spider, after
        # it has processed the response.

        # Must return an iterable of Request, or item objects.
        for i in result:
            yield i

    def process_spider_exception(self, response, exception, spider):
        # Called when a spider or process_spider_input() method
        # (from other spider middleware) raises an exception.

        # Should return either None or an iterable of Request or item objects.
        pass

    def process_start_requests(self, start_requests, spider):
        # Called with the start requests of the spider, and works
        # similarly to the process_spider_output() method, except
        # that it doesn’t have a response associated.

        # Must return only requests (not items).
        for r in start_requests:
            yield r

    def spider_opened(self, spider):
        spider.logger.info('Spider opened: %s' % spider.name)


class SipderworkscrapyDownloaderMiddleware:
    # Not all methods need to be defined. If a method is not defined,
    # scrapy acts as if the downloader middleware does not modify the
    # passed objects.
    # 如果下载器返回的html中的纯文本不足二百个字符，那就启动selenium得到渲染之后的页面
    def __init__(self):
        # print('Chrome driver begin...')
        options = webdriver.ChromeOptions()
        options.add_argument('--headless')  # 设置无界面
        self.webdriver = webdriver.Chrome(options=options)

    def __del__(self):
        self.webdriver.close()  # 关闭窗口
        self.webdriver.quit()  # 关闭浏览器

    @classmethod
    def from_crawler(cls, crawler):
        # This method is used by Scrapy to create your spiders.
        s = cls()
        crawler.signals.connect(s.spider_opened, signal=signals.spider_opened)
        return s

    def process_request(self, request, spider):
        # Called for each request that goes through the downloader
        # middleware.

        # Must either:
        # - return None: continue processing this request
        # - or return a Response object
        # - or return a Request object
        # - or raise IgnoreRequest: process_exception() methods of
        #   installed downloader middleware will be called
        return None

    def process_response(self, request, response, spider):
        # Called with the response returned from the downloader.
        # print(response)
        # print('download begin...')
        try:
            pure_text = BeautifulSoup(response.body).get_text()
            if len(pure_text) < 200:
                print('Chrome driver begin...')
                self.webdriver.get(url=response.url)
                # wait = WebDriverWait(self.webdriver, timeout=20)
                return HtmlResponse(url=response.url, body=self.webdriver.page_source,
                                    encoding='utf-8')  # 返回selenium渲染之后的HTML数据
            else:
                return response
        except TimeoutException:
            return HtmlResponse(url=response.url, encoding='utf-8', status=500)
        finally:
            print('Chrome driver end...')

        # Must either;
        # - return a Response object
        # - return a Request object
        # - or raise IgnoreRequest
        # return response

    def process_exception(self, request, exception, spider):
        # Called when a download handler or a process_request()
        # (from other downloader middleware) raises an exception.

        # Must either:
        # - return None: continue processing this exception
        # - return a Response object: stops process_exception() chain
        # - return a Request object: stops process_exception() chain
        pass

    def spider_opened(self, spider):
        spider.logger.info('Spider opened: %s' % spider.name)
